1. Field of the Invention
The present invention relates to an image-forming apparatus having an image-forming unit for forming a copying image on the basis of an exposed image of an original. More specifically, the invention relates to an image-forming apparatus with an exposure-light intensity adjusting function for preventing an image on an opposite surface from being formed as the copying image.
2. Description of the Related Art
Recently, both sides of an original are being provided with images to use the resources effectively in consideration of environmental problems. If the transmittance of the two-sided original is high when an image-forming apparatus, e.g., a plain paper copying machine, makes a copying image, then the image of the opposite side may be copied with the image of the front side. Thus, an operator has to adjust an exposure light intensity manually so that the image of the opposite side is not copied.
Many plain paper copying machines have an automatic copy density control function, as disclosed in U.S. Pat. No. 4,573,787. This function is useful to regulate the density of a copying image even if each density of originals differs from each other. However, this function is not helpful to prevent an image on the opposite surface from being copied.